Distribution gear mechanisms in a motor vehicle serve for variable distribution of the drive moment to the two vehicle axles. For this, the distribution gear mechanism has an input shaft, a first output shaft and a second output shaft. The input shaft is connected to a drive unit of the motor vehicle, such as, for example, an internal combustion engine. The first output shaft is connected via a first axle differential to a first axle of the motor vehicle, such as, for example, the rear axle. The second output shaft is connected via a second axle differential to a second axle of the motor vehicle, such as, for example the front axle.
The distribution gear mechanism further includes a torque transmission device having a clutch in order to distribute optionally to the first output shaft and the second output shaft a drive moment which is introduced via the input shaft. For example, the first output shaft may be formed integrally with or connected rotationally fixedly to the input shaft, in which a friction clutch variably couples the input shaft optionally also to the second output shaft. Alternatively, it is possible for example for the torque transmission device to include an intermediate axle differential gear mechanism, in which a friction clutch is active between the input shaft and one of the two output shafts (or between both output shafts) in order to block the intermediate axle differential gear mechanism optionally in a variable manner.
The input shaft and the second output shaft are usually arranged at different heights, wherein an offset drive is provided between the torque transmission device and the second output shaft. This offset drive may be formed as a chain drive having a lower sprocket and an upper sprocket which are connected via a chain. The lower sprocket is coupled rotationally fixedly with the second output shaft. The upper sprocket is coupled rotationally fixedly with an output element of the torque transmission device. Alternatively, the connection is created via gear stages.
In order for the distribution mechanism not to require its own oil pump, the chain of the chain drive may serve as an oil conveyor device. For this, the lower sprocket engages in an oil sump which is filled with lubricating oil, in which lubricating oil is conveyed from the oil sump in the direction of the upper sprocket by means of the chain. At the upper end of the chain drive, the lubricating oil is flung off the chain and may then, for example, be captured by a capture device and from there conducted in the direction of the lubrication points (e.g., friction clutch and bearings).
One disadvantage of known distribution gear mechanisms is that the lower sprocket engaging in the oil sump, or the bottom gear stage, which is guided through the oil sump, causes undesirable splash losses, i.e., the drag moment occurring in the oil sump reduces the efficiency of the distribution gear mechanism. Also, as a result the temperature of the lubricating oil in the oil sump is increased so that the cooling effect of the lubricating oil is reduced.
WO 2012/038022 discloses a distribution gear mechanism which has an outlet opening in the oil reservoir which opens into the oil sump, in which the chain is arranged at the outlet opening of the oil reservoir such that the chain chokes the outflow of lubricating oil, which has collected in the oil reservoir, into the oil sump. The actuator here is not connected to a clutch.